A few years ago, a comedy like Mr. Woodcock — in which a self-help author (Seann William Scott) tries to help his mom (Susan Sarandon) realize that her new fiancé (Billy Bob Thornton), the wicked gym teacher of the title, is the scum of the earth — would’ve played fine. Uninspired, sure, but sporadically, spasmodically funny. But in this post-Apatow-the-arrested-development-genius world, it can’t compete. The only thing worth watching is Sarandon, popping in from a classier reality. C+